Apparatus and method for situ sharpening of bore hole bits

ABSTRACT

An impregnated diamond core bit is sharpened at the bottom of a bore hole, the bit being secured to the outer barrel of coring apparatus attached to a tubular drill string extending to the top of the bore hole. A sharpener is releasably mounted in the lower end of an inner core barrel lowered through the drill string into the outer barrel and latched thereto, with the sharpener projecting below the lower end of the core bit, the sharpener having nozzles for discharging abrasive material pumped through the sharpener against the drilling face of the bit to sharpen the same, whereupon the coring operation can be effected in the usual manner, the core releasing the sharpener from the inner barrel and pushing it upwardly along and within the inner barrel as the core is formed. The sharpener is retrieved with the inner barrel upon release of the latter from the outer barrel and its upward removal through the drill string to the top of the bore hole.

a United States Patent [191 Bridwell APPARATUS AND METHOD FOR SITU SHARPENING OF BORE HOLE BITS [75] Inventor: Harold C. Bridwell, Salt Lake City,

Utah

[73] Assignee: Christensen Diamond Products Company, Salt Lake City, Utah [11 3,818,997 June 25, 1974 Primary ExaminerDavid H. Brown Attorney, Agent, or Firm-Bernard Kriegel 5 7] ABSTRACT An impregnated diamond core bit is sharpened at the bottom of a bore hole, the bit being secured to the outer barrel of coring apparatus attached to a tubular drill string extending to the top of the bore hole. A sharpener is releasably mounted in the lower end of an inner core barrel lowered through the drill string into the outer barrel and latched thereto, with the sharpener projecting below the lower end of the core bit, the sharpener having nozzles for discharging abrasive material pumped through the sharpener against the drilling face of the bit to sharpen the same, whereupon the coring operation can be effected in the usual manner, the core releasing the sharpener from the inner barrel and pushing it upwardly along and within the inner barrel as the core is formed. The sharpener is retrieved with the inner barrel upon release of the latter from the outer barrel and its upward removal through the drill string to the top of the bore hole.

29 Claims, 7 Drawing Figures PATENTEDJUNZSIQM sum 2 or 3 c? a a W 5 APPARATUS AND METHOD FOR SITU SHARPENING OF BORE HOLE BITS nection with the drilling of bore holes through use of a wireline coring method. With this method, an inner core barrel is lowered through a drill string and is releasably latched to an outer core barrel to which a core bit is secured for cutting the annular portion of the bore hole. After the desired length of core has been produced and is located in the inner barrel, it is broken from the formation at the bottom of the hole, with the inner core barrel elevated from the outer core barrel and within the tubular string to the top of the bore hole. Following removal of the core, the inner core barrel is then relowered through the drill string and is latched in appropriate place to the outer core barrel, so that the coring operation can continue with the core bit cutting the annular portion of the formation and producing an additional length of core that moves relatively upwardly within the inner core barrel. I

When using impregnated diamond core bits in connection with wireline coring, the bit is kept sharp to some degree through abrasion of the bit matrix by the formation being cut. However, if the abrasiveness-of the formation is too low, the matrix of the bit is not abraded away sufficiently and the diamonds arenot exposed properly for cutting. Under this condition, the bit will not penetrate the formation at the desired rate and monds is eroded away too rapidly, or, as stated below,

if the formation abrasiveness is too low, the matrix is abraded away insufficiently.

By virtue of the present invention, the bit, and particularly bits of the impregnated diamond type, canbe sharpened at the bottom of the bore hole independently of the formation encountered, thereby eliminating the requirement of attempting to match the abrasiveness of the matrix holding the diamonds t0 the abrasiveness of the formation being drilled. The ability to retain the sharpness of the bit enables the latter to be designed with diamonds held in the matrix for optimum cutting action, rather than designing the bit to match the matrix to the abrasiveness of the formation to be cut. 4

An apparatus and method for sharpening diamond bits at the bottom of the hole eliminates the costly round trips of the bit to the surface of the bore hole for sharpening or to exchange bits. In the case of an impregnated diamond bit, it enables the drill bit to remain at the bottom of the hole until it has been'substantially entirely consumed during the drilling or coring action.

A further objective of the invention is to maintain the bit sharp, and thereby enable it to penetrate the formation faster, reducing coring costs. Moreover, wear and tear on the equipment at the bore hole location is also reduced because of the elimination of the round trips for sharpening or exchanging bits, which further reduces the coring cost.

Another objective of the invention is to provide an apparatus and method for sharpening bits in the bore hole that insures core penetration with a sharp bit and results in the drilling of a straighter hole which, in turn, results in the production of a better or more desirable core for analysis upon its retrieval at the top of the bore hole.

This invention possesses many other advantages and has other objectives which may be made more clearly apparent from a consideration of several forms and methods embodying the invention. These forms and methods are shown and described in the present specification and in the drawings accompanying and constituting a part thereof. They will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that y the line 22 on FIG. 1b;

FIG. 3 is a view similar to FIG. 2, withparts in another position;

,FIG. 4 is a cross sectionv taken along the line 44 on FIG. 2; a

FIG. 5 is a cross-section taken along the line 55 on FIG. 2; and

FIG. 6 is a longitudinal section through a modified form of the invention.

A known type of coring apparatus A is illustrated in the drawings for producing a core C in a bore hole B and for withdrawing the core, as by means of a wireline (not shown), to the top of the bore hole after it has been produced. More specifically, a coring apparatus of the general type illustrated in U.S. Pat. No. 3,127,943 can be provided, which includes a core bit 10 suitably secured to a lower tubular bit shank ll threadedly'attached to the lower end of an outer barrel structure 12, the upper portion of which is constituted by a tubular body member 13, such as a latch coupling sub, having an upper threaded box 14 for attachment to the lower end of a tubular drill string D extending through the bore hole to the surface.

An inner core barrel 15 is disposed within the outer core barrel 12, its lower end being constituted as a shoe 16 containing a core catcher 17 to grip the core C and prevent it from dropping downwardly out of the inner core barrel. The upper end of the core barrel is connected to a sub 18, which, in turn, makes a swivel conupon a suitable lower thrust ball bearingdevice 22 car.-

ried by a lower bearing support 23 threaded onto a mandrel 24, its unthreading being precluded by a suitable lock nut 25 threaded on the mandrel and bearing against the lower support. An upper thrust ball bearing device 26 bears upon the upper side of the internal flange 21, the upper end of the upper thrust bearing engaging an upper mandrel or bearing support 27, the mandrel being suitably secured to a latch body 28 carrying laterally shiftable latches 29 slidable in transverse body slots 30 and urged outwardly into a lock groove 31 in the outer barrel body 13 by helical compression springs 32 acting between the oppositely facing latches 29 to snap them into the lock groove when aligned therewith.

The latches 29 areretracted from the groove 31 by the upward movement of a retracting rod 33 slidable longitudinally in the latch body 28 and having retracting pins 34 thereon disposed in slots 35 in thelatches and adapted to engage tapered cam faces 36 forming one side of each slot. The retracting rod 33 is moved upwardly to effect retraction of the latches from the coupling groove 31 by engagement of a suitable overshot (not shown) with a retracting head 37 attached to the retracting rod by a threaded connection 38 or the like. The latch mechanism forms no part of the present invention, a similar mechanism being illustrated and described in US. Pat. No. 3,437,159. For'that matter, the core barrel and the swivel arrangement also forms no part of the present invention, being illustrated and described in U.S. Pat. No. 3,127,943.

The core bit is of the impregnated diamond bit type, such bit including a mixture of diamond particles andmatrix material all suitably bonded together, in a known manner. An example of an impregnated diamond bit, illustrated somewhat diagrammatically in the drawings, is illustrated and described in US. Pat. No. 3,537,538. It includes the tubular bit shank 11 and a lower impregnated diamond bit portion 10 terminating in V-shaped annular ribs 40, which provide the lower face F of the bit. The bit has an external cylindrical gaugesurface 41 and also an internal cylindrical gauge surface 42 for determining the diameter of the bore hole being drilled and the diameter of the core C formed, which will pass upwardly through the core catcher 17 and into the inner core barrel during the coring operation.

Assuming the outer barrel 12 with the impregnated diamond bit 10, 11 to be disposed in the bore hole B,

the inner core'barrel 15 can be lowered through the drill string D attached to the outer barrel 12 until its latches 29 become aligned with the circumferential groove 31 in the outer barrel sub 13, thereby appropri ately locating the inner barrel in place, as shown in FlGS. 1a, 112. A coring action can now take place with appropriate drilling weight being imposed through the drill string D on the outer barrel l2 and the bit to effect penetration of its cutting face F into the bottom 14 of the bore hole, the drilling string, outer barrel and bit' being appropriately rotated while drilling fluid is being pumped down the drilling string to remove the cuttings being producedJThe drilling fluid will pass from the drill string D around the latch body 18 and into the annular space 43 between the inner and outer core barrels, discharging through suitable waterways (not shown) in the impregnated diamond bit against the bottom 'H of the bore hole, to flush the cuttings from the bottom and upwardly around the exterior of the outer and is positioned in the inner barrel, the core may be broken off atthe lower portion of the barrel by elevating the drill string D, the core catcher 17 moving down the downwardly tapering inner face 44 of the shoe l6 and inwardly against the exterior of the core, gripping the latter and preventing it from dropping out of the barrel 15. The core barrel 15 may now be retrieved by lowering a suitable overshot on a wireline through the drilling string, the overshot becoming coupled to the retracting head 37, enabling an upward pull to be taken thereon to shift the retracting rod 33 upwardly and causing the retracting pins 34 to engage the inclined cam surfaces 36 and shift the latches 29 laterally inwardly fromthe lock groove 31, the'entire mechanism within the outer core barrel 12 being removable through the drill string D to the top of the bore hole.

As disclosed in the drawings, a sharpener apparatus S is illustratedthat enables the drilling face F of the impregnated core bit to be sharpened preparatory to producing the next length of core. As shown, the sharpener apparatus includes a sharpener body having an external diameter 51 slightly less than the inside diameter of the internal cylindrical gauge surface 42 of the bit, the body being hollow and its upper portion being constituted as spring-like latch arms 52 formed by circumferentially spaced longitudinal slots 53 extending from the upper end of the body to a desired extent downwardly thereof, these arms being integral with outwardly extending latch fingers'54 having upper downwardly inclined surfaces 55 and adapted to fit in an internal. circumferential lock groove 56 formed in the lower portion of the inner core barrel l5.

Preparatory to placing the inner core barrel 15 within the drill string,'the sharpener body 50 is moved upwardly into the inner barrel, its latch fingers 54 expanding outwardly into the circumferential lock groove 56, at which time the lower portion 57 of the sharpener body 50 extends downwardly to a predetermined extent below the lower end of the tube shoe 16. A stinger or stem58 extends through a passage 59 in the lower closed end 60 of the sharpener body, such lower end portion being generally frusto-conical; that is, having its external surface 61 tapering in a downward direction. The stem 58 projects initially below the sharpener body, its upper end being suitably attached, as by welding, to a retainer plate 62 which is movable downwardly into the latch arms 52 and behind the latch fingers 54, as determined by engagement of the plate with an upwardly facing shoulder 63 formed on the latch arms, thereby holding the latch fingers in the circumferential lock groove 56. Initially, the stinger 58 and retainer plate 62 will be disposed in an upper position, the plate being located above the latch fingers. After the bodyv 50 has been inserted into the lower end of the.

inner core barrel l5 and the fingers 54 have snapped outwardly into the lock groove 56, the lower end of the stem 58 can be grasped for the purpose of pulling the the annulus 43 between the inner and outer barrel structures into the interior of the inner core barrel 15. This fluid can pass into the sharpener body through a plurality of ports 66 extending throughthe retainer plate 62. Fluid can also be pumped from the lower portion of the inner barrel-outer barrel annulus 43 through lower ports 67 in the sharpener body into a central chamber 68 in the body 50. From this chamber, the fluid can discharge through a plurality of circumferentially spaced, upwardly and outwardly inclined nozzles or passages 70 that are directed toward the drilling face F of the impregnated bit 10, there being a sufficient number of nozzles present to cover the full surface of the lower drilling face of the bit. 'As described further hereinbelow, the nozzles, ports or jets 70 willbe in appropriate position upon the location of the inner core barrel in its normal position within the outer core barrel 12, determined by the outward expansion of the latches 29 into the lock-groove 31 of the outer barrel structure. When in such position, a suitable elastomer seal ring 71 mounted inan external groove 72 in the sharpener body will seal against the internal gauge surface 42 of the bit, causing all of the fluid pumped down through the apparatus to pass into the central chamber 68 and outwardly and upwardly through the nozzles 70 to jet or impinge upon the lower drilling face F of the bit.

The sharpener device S is releasably secured in place within the lower portion of the inner core barrel 15 at the top of the bore hole, the inner core barrel being lowered through the drill string D and into the outer barrel 12, to which it is latched, and with the sharpener nozzles 70 appropriately located for directing the material jetting therefrom against the lower face F of the bit, the seal ring 71 sealing against the inner surface 42 of the bit. At this time, the entire sharpening apparatus and bit are elevated from the bottom of the bore hole being drilled (FIGS. 1a, lb, 2). Fluid is pumped down through the drilling string D, the fluid containing abrasive particles, being circulated down through the annulus 43 between theinner and outer core barrels l5, l2, and also through the port 65 into the inner barrel l5, and through the ports 66 in'the retainer plate, as well as through the sideports 67 in the sharpenerbody, into the chamber 68. The abrasive laden fluid jets through the nozzles 70, impinging upon the lower face F of the bit to sharpen the same by abrading away a portion of the matrix material, in order to expose diamonds embedded in the matrix, thereby sharpening the bit l0.

The abrasive particles used can be of different types, such as aluminum oxide, tungsten carbide, silicon carbide, and/or other abrasive particles, which may be in a size between 50 and 400 mesh. The total abrasive powder required for sharpening may vary, for example, being about 5 pounds, which is poured into the drill string D and then pumped by the circulating fluid downwardly and into the bit sharpener body 50, the particles jetting from the nozzles 70 and striking the face F of the bit to remove the matrix from around the diamonds at the face.

After the abrasive particles have been pumped down into the sharpener body 50, and circulation has continued for a required time, which, for example, may be a few minutes, or sufficient time for all of the abrasive particles to have been jetted through the nozzles against the face of the bit, circulation may be stopped. The drill string D is then lowered a short distance, the

' projecting end of the stinger or stem engaging the botrelatively elevate the plate above the fingers 54 to a released position, the bottom of the sharpener body 50 then engaging the bottom HC of the hole to force the sharpener body upwardly within the inner barrel 15, the latch fingers 54 swinging inwardly from the lock groove 56, the sharpener body moving upwardly until the drilling face F of the bit contacts the bottom H of the bore hole, whereupon coring is initiated, following conventional coring procedures.

During the coring operation, the top of the'core C forces the sharpener S upwardly within the inner barrel 15, the sharpener progressively moving upwardly within the inner barrel on top of the core (FIG. 3). After the desired length of core has been cut by the bit, and it has been broken off, the inner barrel 15 with the core C and sharpener S therewithin is released from the outer barrel 12 by means of the wireline and related devices coupledto the head 37, and elevated through the drill string D to the surface of the bore hole, the core C and the sharpener S then being removed from the barrel l5.

Before lowering the inner barrel structure back into its coring relation to the outer barrel, the sharpener S is reinserted upwardly within the inner barrel and relocked in the internal circumferential lock groove 56.

As disclosed in FIG. 6, the stem 58a has a holding device suitably secured thereto provided with penetrating or gripping points 81 adapted to engage the bottom portion HC of the bore hole. The stem is held in its position in which the retainer plate 62 maintains the latch fingers 54 in the circumferential lock groove 56 by a shear pin 82 extending through the lower portion of the sharpener body 50 and the stinger. After the inner barrel l5 and sharpener S have been latched in appropriate position with respect to the outer barrel 12 and bit 10, the apparatus can be lowered until the holding device 80 engages the bottom HC of the bore hole, which will insure against rotation of the sharpener apparatus S, this apparatus being locked to the inner core 1 barrel 15 which normally does not rotate because of its swivel mounting within the outer barrel 12. During pumping of the abrasive materialthrough the nozzle jets 70, and with the holding points 81 insuring against rotation of thesharpener body 50, the drill string D, outer barrel 12 and bit 10 can be turned at a relatively slowrate to insure that the abrasive fluid jetting from the nozzles will thoroughly cover all required surfaces of the bit face F, to sharpen the latter.

After sharpening has been completed, and rotation of the drill string, outer barrel and bit has ceased, sufficient downweight is imposed on the coring apparatus to shear the pin 82, the coring apparatus A and the sharpener body 50 shifting downwardly with respect to the retainer plate 62 and stem 58a, the plate relatively moving upwardly from its position behind the latch fingers 54, permitting release of the latter after the sharpener body 50 has shifted downwardly into contact with the enlarged holding device 80 attached to the stem. Downward movement of the coring apparatus can continue, the core bit and inner barrel moving downwardly along the sharpener apparatus 8 until the bit face F engages the bottom H of the bore hole. The imposition of the desired drilling weight on the bit, its rotation at the desired speed, and the circulation of drilling fluid downwardly through the apparatus can then continue to produce the core C, which will progressively move the sharpener S and the device 80 upwardly into the barrel, the latter riding on top of the core. After the required core length has been produced, it is broken off at the bottom of the hole, and the inner barrel recovered on a wireline from the outer barrel l2 and through the tubular drill string D to the surface of the bore hole.

In lieu of pumping the abrasive powder downwardly through the drill string and into the sharpener body, as described above, the abrasive powder can be placed in the inner barrel 15 above or inside of the bit sharpener S. This powder is fed into the central chamber 68 of the sharpener body at a desired rate when fluid circulation is established down through the drill string D and through the core barrel apparatus. The abrasive powder particles can be loosely bonded together with a glue the drilling string and including a drill bit for drilling the bore hole; a sharpening device within said drive structure; means positioning said device in the drive structure with the device extending below the lower end of said drill bit, said device including meansfor enabling a sharpening action to be effected on said drill bit while the drive structure is in the bore hole; and releasing means for effecting release of said sharpening device with respect to said drive structure to allow said device to shift relatively upwardly in the drive structure to a position above the lower end of said drill bit to enable said lower end to engage the bottom of the bore hole. 7

2. In apparatus as defined in claim 1; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said sharpening device and allow said sharpening device to be shifted to said position above the lower end of the drill bit in response to downward movement of the drive structure in the bore hole.

3. In apparatus as defined in claim 1; said means for enabling a sharpening action to be effected including a plurality of fluid passages for directing fluent material upwardly against the lower end of said drill bit to sharpen the same.

4. In apparatus as defined in claim 1; said means for enabling a sharpening action to be effected including a plurality of fluid passages for directing fluent material upwardly against the lower end of said drill. bit to sharpen, the same; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said sharpening device and allow said sharpening device to be shifted tosaid position above the lower end of the drill bit in response to downward movement of the drive structure in the bore hole.

5. In apparatus as defined in claim 1; said positioning means being constructed and arranged to permit relative rotation between said drive structure and sharpening device to enable the sharpening action to be effected around the full circumference of said lower end of the drill bit.

6. In apparatus as defined in claim 1; said means for enabling a sharpening action to be effected including a plurality of fluid passages for directing fluent material upwardly .against the lower end of said drill bit to sharpen the same; said positioning means being constructed and arranged to permit relative rotation between said drive structure and sharpening device to enable the fluent material to be directed against said lower end of the drill bit around the full circumference of said lower end. r

7. In apparatus as defined in claim 1; said means for enabling a sharpening action to be effected including a plurality of fluid passages for directing fluent material upwardly against the lower end of said drill bit to sharpen the same; said positioning means being constructed and arranged to permit relative rotation be tween said drive structure and sharpening device to enable the fluent material to be directed against said lower end of the drill bit around the full circumference of said lower end; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said sharpening device and allow said sharpening device to be shifted to said position above the lower end of the drill bit in response to downward movement of the drive structure in the bore hole.

8. In apparatus for effecting sharpening of a core bit at the lower portion of a tubular drilling string disposed ina bore hole: anouter drive structure adapted to be secured to the drilling string and including a core bit for drilling upon the bottom of the bore hole to produce a core therein; an inner core barrel within the outer drive structure to receive the core; a sharpening device within said inner barrel; means positioning said device in said inner barrel with the device extending below the lower end of said core bit, said device including means for enabling a sharpening action to be effected on the lower end of said core bit while the apparatus is in the bore hole; and releasing means for effecting release of said device with respect to said inner barrel to allow said device to shift relatively upwardly in said inner barrel to enable the lower end of said core bit to engage and act upon the bottom of the bore hole and produce the core. 7

9. In apparatus as defined in claim 8; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said device and allow said sharpening device to be shifted relatively upwardly in said inner barrel, the core formed engaging said sharpening device to relatively shift said sharpening device relatively upwardly within and along said inner barrel toward the upper end of said'inner barrel.

10. In apparatus as defined in claim 8; said means for enabling a sharpening action to be effected including a plurality of circumferentially spaced passages for directing fluent material upwardly against the lower end of said core bit to sharpen the same.

11. In apparatus as defined in claim 8; said means for enabling a sharpening action to be effected including a plurality of circumferentially spaced passages for directing fluent material upwardly against the lower end of said core bit to sharpen the same; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said device and allow said sharpening device to be shifted relatively upward in said inner barrel, the core formed engaging said sharpening device to relatively shift said sharpening device relatively upwardly within and along said inner barrel toward the upper end of said inner barrel.

12. In apparatus as defined in claim 8; said positioning means being constructed and arranged to permit relative rotation between said outer drive structure and said sharpening device to enable the sharpening action to be effected around the full circumference of said core bit.

13. In apparatus as defined in claim 8; said means for enabling a sharpening action to be effected including a plurality of circumferentially spaced passages for directing fluent material upwardly against the lower end of said core bit to sharpen the same; said positioning means being constructed and arranged to permit rela tive rotation between said outer drive structure and said sharpening device to enable the fluent material to be directed against said lower end of the core bit around the full circumference of said lower end.

14. In apparatus as defined in claim 8; said means for enabling a sharpening action to be effected including a plurality of circumferentially spaced passages for directing fluent material upwardly against the lower end of said core bit to sharpen the same; said positioning means being constructed and arranged to permit relative rotation between said outer drive structure and said sharpening device to enable the fluent material to be directed against said lower end of the core bit around the full circumference of said lower end; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said device and allow said sharpening device to be shifted relatively upwardly in said inner barrel, the core formed engaging said'sharpening device to relatively shift said sharpening device relatively upwardly within and along said inner barrel toward the upper end of said inner barrel.

15. In apparatus as defined in claim 8; and means releasably securing said inner core barrel. within said outer drive structure, whereby said inner core barrel and sharpening device are movable downwardly through the drilling string to operative position within the outer drive structure and upwardly from the outer .drive structure through the drilling string to the top of the bore hole.

16. In apparatus as defined in claim 8; said means for enabling a sharpening action to be effected including a plurality of circumferentially spaced passages for directing fluent material upwardly against the lower end of said core bit to sharpen the same; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said device and allow said sharpening device to be shifted relatively upward in said inner barrel, the core formed engaging said sharpening device to relatively shift said sharpening device relatively upwardly within and along said inner barrel toward the upper end of said inner barrel; and means releasably securing said inner core barrel within said outer drive structure, whereby said inner, core barrel and sharpening device are movable downwardly through the drilling string to operative position within the outer drive structure and upwardly from the outer drive structure through the drilling string to the top of the bore hole.

17. In apparatus as defined in claim 8; said means for enabling a sharpening action to be effected including a plurality of circumferentially spaced passages for directing fluent material upwardly against the lower end of said core bit to sharpen the same; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said device and allow said sharpening device to be shifted relatively upward in said inner barrel, the

core formed engaging said sharpening device to relatively shift said sharpening device relatively upwardly within and along said inner barrel toward the upper end of said inner barrel; means releasably securing said inner core barrel within said outer drive structure, whereby said inner core barrel and sharpening device are movable downwardly through the drilling string to operative position within the outer drive structure and upwardly from the outer drive structure through the drilling string to the top of the bore hole; and passage means for directing the fluent material from the drilling string through the inner barrel and outer drive structure for discharge through the circumferentially spaced passages.

18. In apparatus as defined in claim 8; said means for enabling a sharpening action to be effected including a plurality. of circumferentially spaced passages for directing fluent material upwardly against the lower end of said core bit to sharpen the same; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said device and allow said sharpening device to be shifted relatively upward in said inner barrel, the core formed engaging said sharpening device to relatively shift said sharpening device relatively upwardly within and along said inner barrel toward the upper end of said inner barrel; means releasably securing said inner core barrel within said outer drive structure, whereby said inner core barrel and sharpening device are movable downwardly through the drilling string to operative position within the outer drive structure and upwardly from the outer drive structure through the drilling string to the top of the bore hole; and passage means for directing the fluent material from the drilling string through the inner barrel and outer drive structure for discharge through the circumferentially spaced passages; said core bit being an impregnated diamond bit having a lower drilling face against which the fluent material is directed to sharpen the same.

19. The method of sharpening a drill bit at the lower portion of a drilling string disposed in a bore hole, comprising lowering a sharpening device through the drilling string to a position in which the lower portion of the device extends below the lower end of the drill bit, and then directing'a sharpening medium from said device against the drill bit to sharpen the same.

20. The method as defined in claim 19; in which the sharpening medium embodies a fluent material pumped from the sharpening device and directed from the device against the lower face of the drill bit.

21. The method as defined in claim 19; and relatively rotating the drill bit and sharpening device to direct the sharpening medium against the full circumference of the drill bit. I

22. The method as defined in claim' 19; the sharpening device having circumferentially spaced nozzles directed upwardly toward the lower face of the drill bit, the sharpening medium embodying a fluent material 1'1 pumped through the nozzles against the lower drill bit face.

23. The method of sharpening a core bit connected to an outer drive structure secured to a tubular drilling string disposed in a bore hole, an inner core barrel being adapted to be disposed in the drive structure with a sharpening device located in the lower portion of the inner barrel and with the lower portion of the device extending below the lower end of the inner barrel, comprising lowering the inner barrel and device through the tubular drilling string to a position in which the inner barrel is disposed within the outer structure with the device extending below the lower face of the core bit, then directing a sharpening medium from said device against the lower face to sharpen the same, and shifting the device upwardly in'the inner barrel to enable the core bit to contact the bottom of the bore hole and form the core for movement into the inner barrel.

24. The method as defined in claim 23; the sharpening device having circumferentially spaced nozzles directed upwardly toward the lower face of the drill bit, and pumping the sharpening medium which embodies a fluent material through the nozzles against the lower drill bit face.

25. The method as defined in claim 23, releasably securing the sharpening device in the lower portion of the inner barrel prior to lowering the inner barrel and device through the tubular drilling string, and lowering the apparatus in the bore hole, after the core bit has been sharpened, to engage the sharpening device with the bottom of the bore hole to release the sharpening device from the inner barrel and relatively move the sharpening device upwardly within the inner barrel.

26. The method as defined in claim 23; releasably securing the sharpening device in the lower portion of the inner barrel prior to lowering the inner barrel and device through the tubular drilling string, and lowering the apparatus in the bore hole, after the core bit has been sharpened, to engage the sharpening device with the bottom of the bore hole to release the sharpening device from the inner barrel and relatively move the sharpening device upwardly within the inner barrel; the sharpening device having circumferentially spaced nozzles directed upwardly toward the lower face of the drill bit, and pumping the sharpening medium which embodies a fluent material through the nozzles against the lower drill bit face.

27. The method as defined in claim 23; releasably securing the sharpening device in the lower portion of the inner barrel prior to lowering the inner barrel and device through the tubular drilling string, releasably securing the inner barrel within the outer structure with the sharpening device projecting below the lower face of the core bit, lowering the apparatus in the bore hole, after the core bithas been sharpened, to engage the sharpening device with the bottom of the bore hole to release the sharpening device from the inner barrel and relatively move the sharpening device upwardly within the inner barrel, and releasing the inner barrel to permit the inner barrel, sharpening device and core in the inner barrel to be withdrawn through the drilling string to the top of the bore hole.

28. The method as defined in claim 23; releasably securing the sharpening device in the lower portion of the inner barrel prior to lowering the inner barrel and device through the tubular drilling string, releasably securing the inner barrel within the outer structure with the sharpening device projecting below the lower face of the core bit, lowering the apparatus in the bore hole, after the core bit has been sharpened, to engage the sharpening device with the bottom of the bore hole to release the sharpening device from the inner barrel and relatively move the sharpening device upwardly within the inner barrel, and releasing the inner barrel to permit the inner barrel, sharpening device and core in the inner barrel to be withdrawn through the drilling string to the top of the bore hole; the sharpening device having circumferentially spaced nozzles directed upwardly toward the lower face of the drill bit, and pumping the sharpening medium which embodies a fluent material through the nozzles against the lower drill bit face.

29. The method as defined in claim 23; releasably securing the sharpening device in the lower portion of the inner barrel prior to lowering the inner barrel and device through the tubular drilling string, releasably securing the inner barrel within the outer structure with the sharpening device projecting below the lower face of the core bit, lowering the apparatus in the bore hole, after the core bit has been sharpened, to engage the sharpening device with the bottom of the bore hole to release the sharpening device from the inner barrel and relatively move the sharpening device upwardly within the inner barrel, and releasing the inner barrel to permit the inner barrel, sharpening device and core in the inner barrel to be withdrawn through the drilling string to the top of the bore hole; the sharpening device having circumferentially spaced nozzles directed upwardly toward the lower face of the drill bit, pumping the sharpening medium which embodies a fluent material through the nozzles against the lower drill bit face, and rotating the drilling string and core bit with respect to the inner barrel and sharpening device to direct the fluent material against the full circumference of the lower face of the drill bit. 

1. In apparatus for effecting sharpening of a drill bit at the lower portion of a drilling string disposed in a bore hole: a drive structure adapted to be secured to the drilling string and including a drill bit for drilling the bore hole; a sharpening device within said drive structure; means positioning said device in the drive structure with the device extending below the lower end of said drill bit, said device including means for enabling a sharpening action to be effected on said drill bit while the drive structure is in the bore hole; and releasing means for effecting release of said sharpening device with respect to said drive structure to allow said device to shift relatively upwardly in the drive structure to a position above the lower end of said drill bit to enable said lower end to engage the bottom of the bore hole.
 2. In apparatus as defined in claim 1; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said sharpening device and allow said sharpening device to be shifted to said position above the lower end of the drill bit in response to downward movement of the drive structure in the bore hole.
 3. In apparatus as defined in claim 1; said means for enabling a sharpening action to be effected including a plurality of fluid passages for directing fluent material upwardly against the lower end of said drill bit to sharpen the same.
 4. In apparatus as defined in claim 1; said means for enabling a sharpening action to be effected including a plurality of fluid passages for directing fluent material upwardly against the lower end of said drill bit to sharpen the same; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said sharpening device and allow said sharpening device to be shifted to said position above the lower end of the drill bit in response to downward movement of the drive structure in the bore hole.
 5. In apparatus as defined in claim 1; said positioning means being constructed and arranged to permit relative rotation between said drive structure and sharpening device to enable the sharpening action to be effected around the full circumference of said lower end of the drill bit.
 6. In apparatus as defined in claim 1; said means for enabling a sharpening action to be effected including a plurality of fluid passages for directing fluent material upwardly against the lower end of said drill bit to sharpen the same; said positioning means being constructed and arranged to permit relative rotation between said drive structure and sharpening device to enable the fluent material to be directed against said lower end of the drill bit around the full circumference of said lower end.
 7. In apparatus as defined in claim 1; said means for enabling a sharpening action to be effected including a plurality of fluid passages for directing fluent material upwardly against the lower end of said drill bit to sharpen the same; said positioning means being constructed and arranged to permit relative rotation between said drive structure and sharpening device to enable the fluent material to be directed against said lower end of the drill bit around the full circumference of said lower end; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said sharpening device and allow said sharpening device to be shifted to said position above the lower end of the drill bit in response to downward movement of the drive structure in the bore hole.
 8. In apparatus for effecting sharpening of a core bit at the lower portion of a tubular drilling string disposed in a bore hole: an outer drive structure adapted to be secured to the drilling string and including a core bit for drilling upon the bottom of the bore hole to produce a core therein; an inner core barrel within the outer drive structure to receive the core; a sharpening device within said inner barrel; means positioning said device in said inner barrel with the device extending below the lower end of said core bit, said device including means for enabling a sharpening action to be effected on the lower end of said core bit while the apparatus is in the bore hole; and releasing means for effecting release of said device with resPect to said inner barrel to allow said device to shift relatively upwardly in said inner barrel to enable the lower end of said core bit to engage and act upon the bottom of the bore hole and produce the core.
 9. In apparatus as defined in claim 8; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said device and allow said sharpening device to be shifted relatively upwardly in said inner barrel, the core formed engaging said sharpening device to relatively shift said sharpening device relatively upwardly within and along said inner barrel toward the upper end of said inner barrel.
 10. In apparatus as defined in claim 8; said means for enabling a sharpening action to be effected including a plurality of circumferentially spaced passages for directing fluent material upwardly against the lower end of said core bit to sharpen the same.
 11. In apparatus as defined in claim 8; said means for enabling a sharpening action to be effected including a plurality of circumferentially spaced passages for directing fluent material upwardly against the lower end of said core bit to sharpen the same; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said device and allow said sharpening device to be shifted relatively upward in said inner barrel, the core formed engaging said sharpening device to relatively shift said sharpening device relatively upwardly within and along said inner barrel toward the upper end of said inner barrel.
 12. In apparatus as defined in claim 8; said positioning means being constructed and arranged to permit relative rotation between said outer drive structure and said sharpening device to enable the sharpening action to be effected around the full circumference of said core bit.
 13. In apparatus as defined in claim 8; said means for enabling a sharpening action to be effected including a plurality of circumferentially spaced passages for directing fluent material upwardly against the lower end of said core bit to sharpen the same; said positioning means being constructed and arranged to permit relative rotation between said outer drive structure and said sharpening device to enable the fluent material to be directed against said lower end of the core bit around the full circumference of said lower end.
 14. In apparatus as defined in claim 8; said means for enabling a sharpening action to be effected including a plurality of circumferentially spaced passages for directing fluent material upwardly against the lower end of said core bit to sharpen the same; said positioning means being constructed and arranged to permit relative rotation between said outer drive structure and said sharpening device to enable the fluent material to be directed against said lower end of the core bit around the full circumference of said lower end; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said device and allow said sharpening device to be shifted relatively upwardly in said inner barrel, the core formed engaging said sharpening device to relatively shift said sharpening device relatively upwardly within and along said inner barrel toward the upper end of said inner barrel.
 15. In apparatus as defined in claim 8; and means releasably securing said inner core barrel within said outer drive structure, whereby said inner core barrel and sharpening device are movable downwardly through the drilling string to operative position within the outer drive structure and upwardly from the outer drive structure through the drilling string to the top of the bore hole.
 16. In apparatus as defined in claim 8; said means for enabling a sharpening action to be effected including a plurality of circumferentially spaced passages for directing fluent material upwardly against the lower end of said core bit to sharpen the same; said releasing means prOjecting below said sharpening device and being engageable with the bottom of the bore hole to release said device and allow said sharpening device to be shifted relatively upward in said inner barrel, the core formed engaging said sharpening device to relatively shift said sharpening device relatively upwardly within and along said inner barrel toward the upper end of said inner barrel; and means releasably securing said inner core barrel within said outer drive structure, whereby said inner core barrel and sharpening device are movable downwardly through the drilling string to operative position within the outer drive structure and upwardly from the outer drive structure through the drilling string to the top of the bore hole.
 17. In apparatus as defined in claim 8; said means for enabling a sharpening action to be effected including a plurality of circumferentially spaced passages for directing fluent material upwardly against the lower end of said core bit to sharpen the same; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said device and allow said sharpening device to be shifted relatively upward in said inner barrel, the core formed engaging said sharpening device to relatively shift said sharpening device relatively upwardly within and along said inner barrel toward the upper end of said inner barrel; means releasably securing said inner core barrel within said outer drive structure, whereby said inner core barrel and sharpening device are movable downwardly through the drilling string to operative position within the outer drive structure and upwardly from the outer drive structure through the drilling string to the top of the bore hole; and passage means for directing the fluent material from the drilling string through the inner barrel and outer drive structure for discharge through the circumferentially spaced passages.
 18. In apparatus as defined in claim 8; said means for enabling a sharpening action to be effected including a plurality of circumferentially spaced passages for directing fluent material upwardly against the lower end of said core bit to sharpen the same; said releasing means projecting below said sharpening device and being engageable with the bottom of the bore hole to release said device and allow said sharpening device to be shifted relatively upward in said inner barrel, the core formed engaging said sharpening device to relatively shift said sharpening device relatively upwardly within and along said inner barrel toward the upper end of said inner barrel; means releasably securing said inner core barrel within said outer drive structure, whereby said inner core barrel and sharpening device are movable downwardly through the drilling string to operative position within the outer drive structure and upwardly from the outer drive structure through the drilling string to the top of the bore hole; and passage means for directing the fluent material from the drilling string through the inner barrel and outer drive structure for discharge through the circumferentially spaced passages; said core bit being an impregnated diamond bit having a lower drilling face against which the fluent material is directed to sharpen the same.
 19. The method of sharpening a drill bit at the lower portion of a drilling string disposed in a bore hole, comprising lowering a sharpening device through the drilling string to a position in which the lower portion of the device extends below the lower end of the drill bit, and then directing a sharpening medium from said device against the drill bit to sharpen the same.
 20. The method as defined in claim 19; in which the sharpening medium embodies a fluent material pumped from the sharpening device and directed from the device against the lower face of the drill bit.
 21. The method as defined in claim 19; and relatively rotating the drill bit and sharpening device to direct the sharpening medium against the full circumference of the drill bit.
 22. The method as defined in claim 19; the sharpening device having circumferentially spaced nozzles directed upwardly toward the lower face of the drill bit, the sharpening medium embodying a fluent material pumped through the nozzles against the lower drill bit face.
 23. The method of sharpening a core bit connected to an outer drive structure secured to a tubular drilling string disposed in a bore hole, an inner core barrel being adapted to be disposed in the drive structure with a sharpening device located in the lower portion of the inner barrel and with the lower portion of the device extending below the lower end of the inner barrel, comprising lowering the inner barrel and device through the tubular drilling string to a position in which the inner barrel is disposed within the outer structure with the device extending below the lower face of the core bit, then directing a sharpening medium from said device against the lower face to sharpen the same, and shifting the device upwardly in the inner barrel to enable the core bit to contact the bottom of the bore hole and form the core for movement into the inner barrel.
 24. The method as defined in claim 23; the sharpening device having circumferentially spaced nozzles directed upwardly toward the lower face of the drill bit, and pumping the sharpening medium which embodies a fluent material through the nozzles against the lower drill bit face.
 25. The method as defined in claim 23, releasably securing the sharpening device in the lower portion of the inner barrel prior to lowering the inner barrel and device through the tubular drilling string, and lowering the apparatus in the bore hole, after the core bit has been sharpened, to engage the sharpening device with the bottom of the bore hole to release the sharpening device from the inner barrel and relatively move the sharpening device upwardly within the inner barrel.
 26. The method as defined in claim 23; releasably securing the sharpening device in the lower portion of the inner barrel prior to lowering the inner barrel and device through the tubular drilling string, and lowering the apparatus in the bore hole, after the core bit has been sharpened, to engage the sharpening device with the bottom of the bore hole to release the sharpening device from the inner barrel and relatively move the sharpening device upwardly within the inner barrel; the sharpening device having circumferentially spaced nozzles directed upwardly toward the lower face of the drill bit, and pumping the sharpening medium which embodies a fluent material through the nozzles against the lower drill bit face.
 27. The method as defined in claim 23; releasably securing the sharpening device in the lower portion of the inner barrel prior to lowering the inner barrel and device through the tubular drilling string, releasably securing the inner barrel within the outer structure with the sharpening device projecting below the lower face of the core bit, lowering the apparatus in the bore hole, after the core bit has been sharpened, to engage the sharpening device with the bottom of the bore hole to release the sharpening device from the inner barrel and relatively move the sharpening device upwardly within the inner barrel, and releasing the inner barrel to permit the inner barrel, sharpening device and core in the inner barrel to be withdrawn through the drilling string to the top of the bore hole.
 28. The method as defined in claim 23; releasably securing the sharpening device in the lower portion of the inner barrel prior to lowering the inner barrel and device through the tubular drilling string, releasably securing the inner barrel within the outer structure with the sharpening device projecting below the lower face of the core bit, lowering the apparatus in the bore hole, after the core bit has been sharpened, to engage the sharpening device with the bottom of the bore hole to release the sharpening device from the inner barrel and relatively move the sharpening device upwArdly within the inner barrel, and releasing the inner barrel to permit the inner barrel, sharpening device and core in the inner barrel to be withdrawn through the drilling string to the top of the bore hole; the sharpening device having circumferentially spaced nozzles directed upwardly toward the lower face of the drill bit, and pumping the sharpening medium which embodies a fluent material through the nozzles against the lower drill bit face.
 29. The method as defined in claim 23; releasably securing the sharpening device in the lower portion of the inner barrel prior to lowering the inner barrel and device through the tubular drilling string, releasably securing the inner barrel within the outer structure with the sharpening device projecting below the lower face of the core bit, lowering the apparatus in the bore hole, after the core bit has been sharpened, to engage the sharpening device with the bottom of the bore hole to release the sharpening device from the inner barrel and relatively move the sharpening device upwardly within the inner barrel, and releasing the inner barrel to permit the inner barrel, sharpening device and core in the inner barrel to be withdrawn through the drilling string to the top of the bore hole; the sharpening device having circumferentially spaced nozzles directed upwardly toward the lower face of the drill bit, pumping the sharpening medium which embodies a fluent material through the nozzles against the lower drill bit face, and rotating the drilling string and core bit with respect to the inner barrel and sharpening device to direct the fluent material against the full circumference of the lower face of the drill bit. 